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Pacific Proving Ground search areas and security zones
for Operation CASTLE.
Fallout predictions were based on weather observations and on the results of previous operations, primarily those in Nevada, for which the
most data were available.
Two types of analyses of weather~wind data were
used in preparing the fallout predictions:
hodographs and trajectory fore-
casts of the paths that would be assumed by particles falling from a given
height through the various wind layers.
HODOGRAPHS.
A hodograph is a plot of wind speeds and directions.
presents a vector diagram representing the horizontal projection of the
path of a wind-sounding balloon rising in the atmosphere at a constant
rate.
The hodograph may also be considered to represent the horizontal
109
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